The field of the invention is automated controls in an industrial environment and more specifically automatic regulation or limitation of industrial machine operations when a person enters restricted facility locations.
In the manufacturing industry, one primary cost associated with manufacturing processes is labor. For this reason, the manufacturing industry is always searching for ways in which to reduce the amount of labor required to produce products. One way to reduce labor costs has been to configure machinery that can accomplish many of the tasks traditionally performed by factory workers. Recent developments in factory automation have resulted in factories where most tasks are performed by automated computer controlled machinery which has reduced labor costs appreciably. In fact, in many manufacturing facilities a large percentage of labor costs are now associated with machine/controller programming and maintenance tasks. For instance, a maintenance engineer may routinely visit various machines within a facility to observe machine operations and, in many cases, to cause machines to perform various maintenance cycles that are designed to render machine operating problems obvious. While fully and partially automated facilities have many advantages, such facilities still have several shortcomings.
To this end, in most automated facilities there are many areas proximate facility machines that are considered relatively hazardous. For example, a drill press for boring holes into metallic components has a drill head that follows a stroke path during a machining cycle. In this case, at least during a drilling stroke operation, the stoke path is typically considered a hazardous area. As another example, on an automotive assembly line where a transfer line moves partially assembled vehicles from one assembly line station to another between assembly processes, during vehicle transfer it may be hazardous for a tool cart or the like to be located between two vehicles that move along the transfer path.
There are several solutions that can be used to at least substantially minimize the potential problems that may be caused by moving machines in an automated environment. One solution for substantially reducing potential problems is to assign a facility employee to visually determine if safe conditions exist prior to allowing machine operations to occur. This solution has the advantage that the employee can react to unforeseen circumstances and make judgment calls regarding what comprises hazardous conditions. The problem with an employee based solution however, is that this solution is counter to the general goal of reducing labor costs through automation. In addition, in this case, there is a risk that an employee may use poor judgment under certain circumstances. The instances of poor judgment are likely to be great in mundane and relatively boring jobs such as monitoring repetitive machine operations.
Another solution for reducing hazards in an automated facility is to effectively build a physical barrier about relatively hazardous locations and areas proximate machines and restrict access to those areas. In this regard, for instance, a cage may be constructed about a machine to keep facility employees out of a restricted machine zone adjacent the machine. Here, entry into the machine zone may be limited to a single entry way that is kept locked unless affirmatively unlocked by a facility employee. For instance, a maintenance employee may want to enter the restricted zone to observe some machine operations from a particularly advantageous vantage point. Here, the maintenance employee would have to unlock the single entry into the zone to gain access to the zone. It is presumed that, by unlocking the entry, the employee is affirmatively acknowledging that the employee is responsible for activities that occur within the zone and that the employee will be vigilant to make sure activities will be limited to non-hazardous activities. Cages and other mechanical zone restricting barriers will be referred to hereinafter collectively as “physical barriers” unless indicated otherwise.
In order to further enhance safety within machine zones the automated industry has developed emergency stop systems that allow facility employees to signal when potentially hazardous conditions exist after the employee enters a restricted machine zone. Where a hazard is signaled, the emergency stop causes machines to assume parked or “fail safe” conditions. To this end, one emergency stop system includes an operating device that is tethered to a machine controller. The operating device typically includes a lever member that has three general positions including deactivated, partially activated and fully activated. As the labels imply, when in the deactivated position the lever is not depressed, when in the partially activated position the lever is depressed to within a specific mid-level range of activation and when in the fully activated position the lever is depressed to within a range of activation that exceeds the mid-level range.
In this type of system, at least some machine operations are allowed when the operator is in the partially activated mode. However, when the operator is in either the fully activated mode or the deactivated mode, machine operations are restricted to only operations considered to be non-hazardous while a person is within the restricted machine zone. In some cases non-hazardous operation includes completely halting machine operations. Thus, if a potential hazard occurs while a person is inside the machine zone, the person can simply either fully activate or else deactivate the operator thereby causing the machine to assume a parked condition.
In addition to employing hardware systems to reduce the likelihood of a hazard, many facilities adopt safety policies designed to mitigate hazards. For instance, in the case of a machine zone restricted by a physical barrier, many facilities adopt a policy whereby only a single person is allowed into a machine zone at a time. For instance, in one case, the entry way into a zone may be equipped with a light curtain sensing device that senses when a person passes therethrough. After one person passes through the entry way the system may monitor for other persons passing through the entry way and, when another person is detected, the system may cause the machines to assume parked positions or some other non-hazardous operating conditions.
Another solution to reduce the likelihood of hazardous conditions has been to restrict machine operations to a sub-set of normal machine operations or a set of operations that is different than the normal set when an employee is proximate a machine or a group of machines where the restricted set of operations are generally considered non-hazardous. Here, the restricted set is typically chosen so as to be exemplary of machine operations so that a maintenance engineer, for instance, can either observe the machine performing important cycles or can cause the machine to cycle through various cycles and get a good sense of how the machine operates during normal operations. In some cases operations may be restricted when an employee opens a door to enter a physically barriered space proximate operating machines. In other cases where physical barriers are not provided, some type of presence sensors may be provided to sense when an employee is located within a space proximate machines and restrict machine operations accordingly. For instance, presence sensor may take the form of pressure sensing pads on the floor proximate a machine(s), motion sensors, thermal sensor, etc. In still other cases, combinations of physical barriers and presence sensors may be combined to determine when an employee is in a zone in which operations should be restricted. For instance, a cage may include a single entry path where a light curtain senses movement and perhaps direction (e.g., in/out) along the path. Here, where a person is detected moving through the path into the restricted space, until a person is detected moving in the opposite direction machine operations may be limited.
Each of the solutions described above has at least one and typically several shortcomings. One problem with physical barrier systems is that the physical barriers (i.e., a cage or the like) are relatively expensive. A related problem is that physical barriers take up space which is often at a premium in a busy manufacturing facility. Another problem with such systems is that access to zones typically has to be through one or a small number of entry ways which can become burdensome when an employee has to access a large number of machine zones during a few hours. In addition, it may be determined during machine operation that a particularly advantageous location from which to view machine operation is obstructed by a physical barrier. One other problem with at least some of the systems described above is that there is no fool proof way to determine when two or more persons are inside a restricted machine zone.
Yet another problem with systems that rely on physical barriers is that such barriers cannot be quickly and easily altered to accommodate changes in machine layout and/or changing juxtapositions of machines within a facility. This shortcoming is becoming more burdensome as manufacturing facilities move toward product customization and away from mass production such that automated machine configurations need to be quickly changeable to accommodate the needs inherent in the manufacture of customized products.
Even if physical barrier configurations did not have the above shortcomings, such configurations are unsuitable for many applications. For instance, in the case of the vehicle transfer line described briefly above, it may be that assembly line workers have to be able to easily move into and out of locations between vehicles (i.e., within the path of the transfer line) on the transfer line during certain portions of a transfer cycle to perform manufacturing operations. Here, providing a mechanical barrier to entry into locations that are only potentially dangerous during some times would be impractical.
Another instance where mechanical boundaries are unsuitable is where a machine zone that is typically not hazardous is rendered potentially hazardous for some reason. In this case, building a mechanical structure about the machine zone would not be cost effective as, after the potentially hazardous circumstances are eliminated, the mechanical structure would serve no purpose. In fact, in many cases hazardous conditions may be able to be eliminated in the time it would take for a physical barrier to be constructed.
Another problem with systems that enforce restricted machine operations when a person is within a specific machine zone is that the restrictions are often too burdensome and eliminate potentially useful capabilities. For example, restricted zones are often selected to be larger than necessary, the thought being that by making the zones larger than required, the chances of hazardous consequences are greatly reduced.
As another example, where machine operations while a person is within a machine zone are limited to a restricted sub-set of normal operations, the restricted sub-set is often too restrictive for the entire zone. For instance, assume a drill press that performs three separate drilling operations at a transfer line station during normal operation, first and second drilling operations along first and second vertical axis and a third drilling operation along a horizontal axis, the drill press rotating from a vertical orientation to a horizontal orientation between the second and third drilling operations. Also assume a restrictive machine zone that surrounds the press.
In this case, when a person is very close to the press, hazard concerns may necessitate restriction of machine operations to a small sub-set of operations including a single reduced speed vertical press operation with the drill turned off (i.e., with a non-rotating drill bit). Here, despite the fact that other operations may be performed without risking a hazard when a person is further removed from the press yet still in the restricted zone, the most restrictive operating requirements (i.e., the restrictions corresponding to locations adjacent the press) must be enforced throughout the zone. This is because zone restricting systems cannot distinguish among locations within the machine zone.
Yet another problem with systems that restrict machine operations when a person is within a restricted machine zone is that there is no way of personalizing operating restrictions as a function of who the person is that enters the zone. In this regard, often different employees within a facility have different duties related to facility machines and therefore have different requirements regarding machine observation. For instance, an industrial processor programmer may have a need to observe different machine cycles than a maintenance engineer. In these cases, ideally, there should be some way of personalizing machine operating restrictions as a function of who, a programmer, a maintenance engineer, etc., enters a restricted machine zone.
Similarly, even among facility employees having the same general titles (e.g., maintenance engineer), certain employees may have more training than others regarding machine operations and therefore should be authorized to be within a machine zone under circumstances that may be inappropriate for other less trained personnel. Here customization of machine operating restraints would be advantageous.